1. Technical Field of the Invention
The present invention relates to cellular telephone systems, the making of frequency plan revisions within such systems and, in particular, to the collection of radio environment statistics data, especially downlink data, that is evaluated in connection with the making of such revisions.
2. Description of Related Art
The following background discussion is presented in the context of some of the frequency plan revision procedures taught by U.S. Pat. No. 6,052,593 (hereinafter referred to as the xe2x80x9cGuimont Patentxe2x80x9d) and U.S. Pat. No. 6,212,386 (hereinafter referred to as the xe2x80x9cBriere Patentxe2x80x9d). The disclosure of each Patent has been incorporated by reference, and thus only a general, very broad, discussion of these procedures is presented herein in order to provide the reader with sufficient background information useful in understanding certain concerns with these procedures that are addressed by the present invention. For a more detailed understanding of these frequency plan revision procedures, the reader is requested to directly consult the Guimont and Briere Patents, as well as other references discussing operations for manual and automatic frequency planning for cellular telephone networks.
Reference is now made to FIG. 1 (which is based on FIG. 2 of the Guimont Patent) illustrating one type of frequency plan revision procedure. In step 100, radio environment statistics measurements are made with respect to a cell. These measurements, made on a cell by cell basis in accordance with known procedures, include a measurement of the uplink interference with respect to not only selected (i.e., currently used) frequencies for that cell, but also candidate (i.e., not currently used, but available) frequencies for that cell. These measurements further include a measurement of uplink and downlink bit error rate.
Next, in step 102, analysis is made of the reported radio environment statistics measurements for a given cell. This analysis is typically referred to as an evaluation, and involves the calculation (either manual or automated), with respect to each sub-frequency group containing selected frequencies, and each sub-frequency group containing candidate frequencies, of the average interference and bit error rate values.
In step 104, the results of the evaluation (step 102) are used to determine a possible frequency plan reshuffling for a given cell. The determined reshuffling of step 104 typically comprises the removal of certain ones of the selected sub-frequency groups which show unacceptable analyzed radio environment statistics measurements, in favor of a replacement with certain ones of the candidate sub-frequency groups which show acceptable analyzed radio environment statistics measurements. Many reshufflings 104 may be determined and considered before settling in step 106 on one or more of the reshufflings. These chosen reshufflings of step 106 are commonly (and hereinafter) referred to as xe2x80x9cproposalsxe2x80x9d for changes in the frequency plan of the cellular telephone system for a certain cell.
Each of the proposals 106 is next submitted for frequency mode validation in step 110 which determines whether the candidate sub-frequency groups within the proposal for a given cell are valid (i.e., fit) with respect to the current physical configuration (i.e., the number and operating capabilities of the included transceivers) of that cell and in particular its base station.
Next, the frequencies within the candidate sub-frequency groups are hypothetically distributed in step 120 to the transceivers of the current cell configuration. Next, a network validation check is made in step 130 on the proposal 106 to determine whether any adverse consequences to the network might arise from an actual (i.e., physical as opposed to hypothetical) implementation of the proposal.
Approved proposals 106 are then submitted in step 150 for pre-update verification which tests for unacceptable interference by considering both the uplink interference radio statistic measurements previously made in step 100 and currently made mobile assisted handoff (MAHO) downlink interference measurements.
A proposal for a cell which is confirmed through pre-update verification is then implemented in step 160 to effectuate a retune of the transceivers in that cell to the frequencies which were assigned in the automatic frequency assignment process of step 120.
Reference is now made to FIG. 2 (which is based on FIG. 2 of the Briere Patent) illustrating another frequency plan revision procedure. The procedure implements a three-pass operation. A first pass, identified generally by arrow 200, is referred to as evaluation. The evaluation pass 200 creates one or more revision proposals for one or more cells in response to the consideration of radio environment statistics measurements which report uplink interference measurements and uplink/downlink bit error rate measurements. A second pass, identified generally by arrow 202, is referred to as pre-update verification. The pre-update verification pass 202 is performed to confirm no more than one proposal for each cell in response to the additional consideration of downlink interference measurements. A third pass, identified generally by arrow 204, is referred to as post-update verification. The post-update verification pass 204 verifies, following network update in accordance with one of the proposals, that network interference levels following the update are satisfactory.
First, a conventional radio environment statistics recording function is used to collect uplink interference measurements and uplink/downlink bit error rate measurements in step 206. The evaluation pass 200 processes the measurements to determine proposed frequency plan reshuffling(s) for a given cell. Next, each proposal is validated against certain validation rules relating, for example, to channel allocation and data required for hand-off. An option (step 210) is then given to request pre-update verification 202 (executed at step 216) for each of the created proposals (using the step 214 made downlink interference measurements and additional step 206 measurements) to narrow the proposal options to one (best or preferred) proposal per cell. Acceptable proposals are then implemented through a network update retune (step 212). An option (step 220) is then given to engage in post-update verification 204 for each of the accepted and implemented proposals. This pass 204 assists the operator in identifying implemented (i.e., deployed) proposals that do not satisfactorily reduce interference and improve network operation. Additional step 214 and step 206 measurements are made and evaluated in step 222 to either (step 224) confirm the deployed proposal or identify (step 226) deployed proposals that should be abandoned through a roll-back in step 228.
Specific attention is now directed to the radio environment statistics measurements (i.e., the data collection efforts) made in connection with frequency revision planning (whether manual or automatic) like those taught above by steps 100 and 150 of FIG. 1, and steps 206 and 214 of FIG. 2. It is important to obtain a sufficient number of data points in order to perform the proposal related calculations (see, for example, the algorithm and particularly step 102 of FIG. 1, and the algorithm and particularly steps 208, 216 and 222 of FIG. 2). Sufficiency is generally not an issue with respect to those measurements made on the uplink by network base stations. The system can configure the base stations, and the base stations typically have enough resources and available time to collect the right amount of data. With respect to downlink measurements, on the other hand, it has been noticed that in some instances the amount of collected downlink data is insufficient to execute the proposal related calculation algorithm.
The reason for this is related to the fact that the downlink measurements are normally made by the mobile stations in connection with their conventional Mobile Assisted Handoff (MAHO) operation. While a mobile station is engaged in a call, the system instructs the mobile station to make the needed frequency plan revision related downlink measurements by borrowing certain measurement opportunities from the MAHO function. If traffic level in a cell is low, this means that mobile stations are not engaged in large number of calls, and thus there is a corresponding reduction in the number of MAHO measurement opportunities where frequency plan revision related downlink measurement data can be collected. Similarly, if the number of frequencies to be measured is high, there maybe insufficient time or resources available to make the required number of downlink measurements.
The foregoing data collection problem is further aggravated by the fact that each proposal related algorithm calculation generally, in accordance with known prior art schemes, considers only that data collected in a most recently completed (i.e., a current) measurement opportunity. That collected data is thereafter processed by the algorithm to determine and implement proposals. Following proposal implementation, the current data is discarded as stale and the procedure repeats itself with a brand new data collection effort and a new execution of the proposal related calculation. If an insufficient amount of data is collected in a given data collection effort, however, then subsequent execution of the proposal related algorithm calculation is abandoned and the entire procedure is repeated starting with a new data collection effort.
What is needed is a mechanism to increase the amount of mobile station collected downlink measurement data that is made available for processing by frequency plan revision procedures.
Radio environment statistics data for determining frequency plan revisions is collected in each of a plurality of separate recording periods. Following conclusion of each recording period, a frequency plan revision algorithm is executed to process the collected radio environment statistics data and determine a frequency plan revision for implementation. The collected data that is considered by the algorithm includes not only that data which was collected in a current one of the recording periods, but also that data collected in previous recording period(s) thereto.
The present invention further comprises a frequency planning tool operable to process separate recording period data collections using a frequency plan revision algorithm in order to determine a frequency plan revision for implementation. The collected data that is considered by the algorithm includes not only that data which was collected in a current one of the recording periods, but also that data collected in previous recording period(s) thereto.
In one specific embodiment of the method and tool of the present invention, the data collected in previous recording periods is considered by the algorithm provided that the quality of the previous data has not been adversely affected by a frequency plan revision implemented during an interim period time between the collection of the data and the execution of the frequency plan revision algorithm.